Heat transfer label



are:

June 23, 1970 J KUNKER, JR ET AL 3,516,842

HEAT TRANSFER LABEL Filed April 27, 1966 FIG. I

RELEASE LAYER PROTECTIVE LAYER PRINT PLASTIC CONTAINER FIG. 2

INVENTORS JOHN J- KL/N/(EE, Jr. ROBE/PT /V. SE/I/SEL, Jr.

3,516,842 Patented June 23, 1970 United States Patent Oflice 3,516,842HEAT TRANSFER LABEL John .I. Klinker, Jr., and Robert N. Sensel, Jr.,Cincinnati, Ohio, assignors to Diamond International Corporation, NewYork, N.Y., a corporation of Delaware Filed Apr. 27, 1966, Ser. No.545,543 Int. Cl. B41m 3/12; B32f 33/00 U.S. Cl. 1173.4 12 ClaimsABSTRACT OF THE DISCLOSURE The present invention relates to a heattransfer decalcomania and, more particularly, to a heat transfer labelparticularly suited for application to a plastic container.

The art of heat transfer decalcomania is an ancient one. Thus the patentto McKerrow No. 1,030,908 discloses a heat transfer label having a paperbacking, a transfer layer of resin or wax, and a design of printing andcolor upon the transfer layer. However, the heat transfer layers ofMcKerrow (note also McKerrow et al. No. 1,161,711) and those whofollowed as exemplified by Rosenfeld No. 1,331,581; Hentschel No.1,882,593; Humphner No. 2,219,071 and Von Hofe No. 2,667,003 have notbeen entirely successful for a number of reasons, particularly whentransferred and applied to plastic containers.

In more recent years a number of other heat transfer labels systems havebeen devised. Thus, the Shepherd Pat. No. 2,862,832 shows a heattransfer decalcomania having only three layers and this decalcomania isindicated to be inexpensive compared with those of the prior art. It hasnow been found, however, that the three layer heat transfer decalcomaniais not commercially satisfactory, particularly when transferred toplastic containers, such as polyethylene bottles, and used as labelsthereon, which labels are subject to the action of scraping, abrasion,weathering and the action of various solvents including detergents. Thelabels of the prior art have proven to be not entirely satisfactory inthat they often fail to pass the simple cellophane-tape test foradhesion (where conventional cellophane adhesive tape such as Scotchtape is placed against the transferred layer and then pulled off, if thecellophane tape partially delaminates the transferred layer from itssubstrate, the coating or laminate has failed the test). These labelshave also failed to provide adequate chemical protection against suchitems as common household liquid detergents. In addition, certain of theprior art transfer labels use, as heat release layers, highly oxidizedaliphatic Waxes which are expensive to use and manufacture.

It is therefore an object of the present invention to obviate and/oralleviate the deficiencies of the prior art, such as indicated above.

It is another object of the present invention to provide a new andimproved heat transfer decalcomania particularly applicable for transferto plastic containers for use as labels thereon.

It is another object of the present invention to provide a highlyaccurate, yet highly resistant label for plastic containers.

It is another object of the present invention to provide a method offorming heat transfer labels.

If is another object of the present invention to provide a label whichis very inexpensive in relation to the transfer labels of the prior art.

It is another object of the present invention to provide a label whichincludes a variety of different types of ink systems.

These and other objects along with the nature and advantages of thepresent invention will be more apparent from the following detaileddescription.

In accordance with the present invention, an essentially five layerheat-transfer decalcomania label similar to that set forth in thecopending application of Klinker, Ser. No. 540,855 filed Apr. 7, 1966,is provided having an inexpensive temporary backing or carrier; a moreinexpensive heat release layer disposed along the upper surface of thetemporary backing; a primer and protective coating disposed upon theupper surface of the heat release layer; a design print which mayinclude a number of layers of different types of inks disposed upon theupper surface of the primer layer; and an overprint adhesive layer.

The heat transfer decalcomania will thus be stratified as shown in FIG.1.

Upon transfer, the label in accordance with the present inventionprovides lasting adhesion to the surface to which it is applied alongwith improved chemical and scuff resistance whereas the heat transferlabels of the prior art often fail to pass the simple cellophane-tapeadhesion test and also fail to provide chemical protection against suchitems as common household liquid detergents.

The temporary backing or carrier for the present label may comprise anysuitable material such as plastic film or metal foil. However, both froma standpoint of expense and ease of handling it has been found mostdesirable to use paper as the carrier. Such paper may be common naturalkraft paper or any other type of paper. While the labels of the priorart have used unsized paper, results were not always satisfactory due torelease layer strike-through unless the paper was either sized orsuper-calendered. However, the paper carrier of the present inventionrequires no special sizing or coating, although coated or sized papermay be used if desired. One material found particularly useful is anexpensive machine-glazed kraft paper.

An improvement of the present invention resides in the heat releaselayer which must generally be a wax-like material which is capable ofsoftening or melting sub stantially during heat transfer so as to permitthe tempo rary backing to separate from the remainder of the label. Inaddition, such material, whether it be a blend or a homogeneousmaterial, must be capable of receiving the primer coat without havingsuch primer sink into or be absorbed by the heat transfer material andwithout caus ing any migration, puddling or crawling of the primer onthe heat release material. The release layer materials used inaccordance with the present invention are also not absorbed by commonmachine-glazed kraft paper thereby permitting such paper to be used asthe carrier.

In particular, the Wax-like release layer of the present invention maytake the form of any one of three following general embodiments:

(I) The release layer may comprise an only slightly oxidized, lowmolecular weight polyethylene wax. As an example, a polyethylene wax hasbeen developed having a M.W. of 1400, a softening point of 103 C., apenetration hardness of 4.0, an acid number of 11.0, a saponificationnumber of only 20, and a viscosity at 250 C. of 225 centipoises. Ingeneral, the saponification number may lie between 15 and 23. Such a waxis much less expensive than the more highly oxidized waxes and inaddition, does not strike-through or become absorbed by commonmachine-glazed kraft paper.

(II) The release layer may comprise an unoxidized hard wax of common andconventional properties having a penetration hardness of about 1-10 anda softening point of about 80120 C., which wax after deposition on thetemporary carrier has been subjected to corona discharge. Such Waxesinclude certain polyethylene waxes (e.g. Epolene N) and someFischer-Tropsch waxes (e.g. FT Wax 200), montan wax, ouricury wax,sterone wax, carnauba wax, certain paraffin waxes, certain microcrystaline waxes, etc.

(III) The release layer may comprise a blend of ethylene-vinyl acetate(EVA) copolymer (e.g. Elvax resin) and parafiin Wax. The blendpreferably comprises 70% paraffin wax and 30% EVA copolymer although theEVA may comprise from -40% of the blend. Various grades of EVA areeffective, regardless of the melt index and molecular weight. Theparaffin wax preferred'is one with a melting point of about 150155 F.

The heat release layer is preferably coated on the backing paper at therate of about 6 lbs. per ream of paper. Thus, if the carrier paperconsists of lbs. machineglazed kraft paper having a thickness of about2.2 mils, the thickness of the heat release layer will be about 0.5 milsor about A of the thickness of the paper backing.

The release wax coated backing paper is then print coated with theprimer and protective coating. This coating is preferably a wax-freevinyl acrylic lacquer or varnish. Such a material is easily printed overthe release layer and in addition forms a good base for the printing ofthe ink design.

The primer and protective coating may be applied to the release layer bythe gravure process and is preferably applied in such a manner so thatits printed area is larger than that of the print to follow. This layerserves two functions in that it provides a primer and foundation for thedesign print and prevents the inks in the design from migrating orstriking into the release layer during label formation. In addition, itprovides chemical and scuff resistance for the label after it has beentransferred.

The design print is coated directly on the primer coating in a mannerdependent upon the exact nature of the design. Thus, the inks utilizedin the design print may vary from one to six colors depending upon thelabel and these separate inks are generally coated or printed inseparate steps. The inks used may be either or both the conventionalnitrocellulose and polyamide type inks.

As a particular aspect of the invention, it has been found that it isparticularly advantageous in that the printing is much easier to controlif the two different ink types are deposited in alternate layers. Thishas been found to reduce the picking and drying problems since thesolvent systems for the two ink types are different.

After the design print has been deposited on the primer coating, anoverprint adhesive layer is then applied on top of the design print. Theadhesive layer comprises a polyamide and is preferably applied as alacquer solution. The adhesive layer is applied in such a manner thatits printed area is larger than that of the design print. The purpose ofthe adhesive layer is to provide adhesion for the label when it istransferred to the labeling surface.

The heat transfer label is utilized by bringing the overprint adhesivelayer in contact with the surface to be labeled, e.g. a plasticcontainer. While the label and the container are in contact, transfer isaccomplished by applying heat and pressure, preferably to the back ofthe temporary carrier. Apparatus for carrying out the transfer may varyconsiderably from the use of a simple electric iron to the apparatusdescribed in the Von Hofe Pat. No. 2,667,003, or the apparatus describedin Bliss Pat. 3,434,- 902.

As heat and pressure are applied to the uncoated side of the temporarybacking so as to press the adhesive layer against the plastic container,the heat release layer will melt or soften and the adhesive overprintwill bond to the labeling surface of the container. After a short periodof time the paper backing is then removed, leaving the adhesiveoverprint, the design print, the protective coating and a portion of theheat release layer strongly attached to the plastic container in amanner shown in FIG. 2.

On the transfer it is found that usually about 50% of the heat releaselayer will be released from the temporary backing.

As heat is applied to the paper carrier two things happen:

First, the transfer coating begins to melt and releases itself from thepaper carrier; and second, the adhesive layer begins to soften andbecomes thermoplastic to bond to the labeling surface. Then the label isreleased from the carrier paper.

When the transfer has been completed the label comprises four permanentlayers as seen by FIG. 2. The adhesive coat, previously the uppermostlayer in FIG. 1, now becomes the bottom layer through which the label isbonded to the labeling surface, e.g. the plastic surface of thecontainer. Immediately above the adhesive is the decorative print layer.Above the print layer and affording chemical and scuff resistancethereto is the protective layer, previously the primer. A portion of therelease coating becomes the uppermost layer and this serves to provideadded chemical and scuff protection.

The present invention may be more clearly understood by reference to thefollowing examples, it being understood that such examples areillustrative only and are not to be considered as limiting of theinvention.

EXAMPLE I A carrier paper made of 30# white machine-glazed kraft paper(secured from Thilmany Paper Company) is coated with a slightly oxidized(saponifiaction number of about 20) wax type polyethylene having amolecular weight of about 1400, a softening point of 103 C., apenetration hardness of about 4.0, an acid number of about 11 and aviscosity of 250 C. of 225 centipoises. The coating on the backing paperis at the rate of 6 lbs. per ream.

The wax coating backing paper is then print coated with a protectivecoating using regular varnish etch cylinder having a depth of 32-40rnicrons--l50 line screen- 15-20 wall with a wax-free vinyl acryliclacquer (98E205 3b, Frederick H. Levey Co., Inc.).

The design print is then printed over the vinyl acrylic layer usingalternate layers of Type C (nitrocellulose) and Type D (polyamide) inks.

Over the ink, as an overprint, there is then coated an adhesive layercomprising a solution of thermoplastic polyamide resin in lacquer form.

A decalcomania, formed as above, is then passed in face-to-face contactwith a polyethylene bottle, the surface of which has been treated torender it more print receptive in a conventional manner, such as byflame contact or corona discharge. Heat and pressure are ap plied to thetemporary backing to effect pressing of the adhesive layer against thepolyethylene. As the heat is applied, the polyethylene layer softenssufficiently to permit removal of the temporary backing. Simultaneously,the adhesive overprint bonds to the polyethylene surface of the bottle.The temporary backing is stripped from the label with about half of therelease layer remaining with the temporary backing and about halfremaining with the label.

After cooling, the bottles so coated are tested to determine theadherence of the label thereto. The label is found to adhere tenaciouslyand to be abrasive resistant and also highly resistant to chemicalaction.

EXAMPLE II The procedure of Example I is carried out with the followingdistinctions. The release layer comprises an unoxidized polyethylene waxhaving a molecular weight of about 1400, a ring and ball softening pointof about 102 C., a penetration hardness of about 4.4 and a viscosity at125 C. of about 190 centipoises. Immediately after deposition of therelease layer, the coated carrier paper is passed beneath a conoradischarge unit to provide the wax with a coated receptive surface.

Decalcomanias of the above type are found to print and to transfer in ahighly satisfactory manner. The resultant products are found to betenaciously adhered and to be highly resistant to both abrasion andchemicals.

EXAMPLE III The procedure of Example I is carried out except that therelease layer comprises a blend of 70% paratfin wax having a meltingpoint 150-155 F. (Sun Oil Co., Grade 5512) and 30% EVA copolymer (DuPont, Elvax 400).

The labels are found to print and to transfer in a highly satisfactorymanner. The resultant products adhere tenaciously and are resistant toboth abrasions and chemicals.

It will be obvious to those skilled in the art that various changes maybe made without departing from the scope of the invention.

What is claimed is:

1. In a heat transfer decalcomania label comprising a temporary backingfor said label, a wax-like heat-release layer on said backing having amelting point of from 80- 120 C. and a penetration hardness of 1-10, awax-free vinyl acrylic primer and protective layer on said heatreleaselayer, a design print on said primer layer, and a polyamide overprintadhesive layer on said print layer, the improvement wherein saidheat-release layer comprises a low-molecular weight polyethylene waxhaving a saponification number between and 23.

2. A label in accordance with claim 1 wherein said temporary backingcomprises machine-glazed kraft paper.

3. A label in accordance with claim 1 wherein said print layer comprisesa plurality of separate layers of alternating nitrocellulose andpolyamide inks.

4. A label in accordance with claim 1 wherein said temporary backingcomprises common natural kraft.

5. A label in accordance with claim 1 wherein the area of said wax-freevinyl acrylic primer and protective layer and said polyamide overprintadhesive layer are greater than the area of said intermediate designprint.

6. A label in accordance with claim 1 wherein said waxlike heat-releaselayer has a thickness of about 0.5 mil.

7. In a heat transfer decalcomania label comprising a temporary backingfor said label, a wax-like heat-release layer on said backing having amelting point of from C. and a penetration hardness of l-10, a wax-freevinyl acrylic primer and protective layer on said heatrelease layer, adesign print on said primer layer, and a polyamide overprint adhesivelayer on said print layer, the imrpovement wherein said heat-releaselayer comprises a blend of an effective quantity of ethylene-vinylacetate copolymer and parafiin wax.

8. A label in accordance with claim 7, wherein said print layercomprises a plurality of separate layers of alternating nitrocelluloseand polyamide inks.

9. A label in accordance with claim 7, wherein said temporary backingcomprises common natural kraft.

10. A label in accordance with claim 7, wherein said wax-likeheat-release layer has a thickness of about 0.5 mil.

11. A label in accordance with claim 7 wherein said heat-release layercomprises said blend of ethylene-vinyl acetate copolymer and paraffinincluding 20-40% of said copolymer and 80-60% of said paraffin wax.

12. A label in accordance with claim 11 wherein said paraffin wax has amelting point of -155 F.

References Cited UNITED STATES PATENTS 2,648,097 8/ 1953 Kritchever.

2,670,555 3/1954 Bostwick et al. 1l73.4 XR 2,746,877 5/1956 Matthes117-3.4 XR 2,862,832 12/1958 Shepherd l17-15 XR 2,894,139 7/1959Magruder et al. 117138.8 2,935,418 5/1960 Berthold et al. 11793.1XR2,970,076 1/1961 Porth 156-240 XR 3,007,829 11/1961 Akkeron 1l7-3.2 X3,014,828 12/1961 Reese 156240 X 3,060,023 10/1962 Burg et al. l173.4 XR3,067,054 12/ 1962 Reese 1173.4 3,245,857 4/ 1966 Rutledge 215-7 XR3,355,348 11/1967 Lamar 11776 X FOREIGN PATENTS 715,914 9/1954 GreatBritain.

WILLIAM D. MARTIN, Primary Examiner H. I. GWINNELL, Assistant ExaminerUS. Cl. X.R.

